A group of migrants recently rescued by Myanmar will be deported to Bangladesh, as the United Nations chief called on regional nations to prioritise saving the lives of those still stranded at sea.

Southeast Asia is currently battling an exodus of boat people fleeing persecution and poverty, with up to 2,000 vulnerable migrants thought to be stranded in the Bay of Bengal, many at the mercy of ruthless people smugglers.

Most are Muslim Rohingyas from the western Rakhine state in Myanmar, where they are not recognised as citizens and instead referred to as "Bengalis" or illegal immigrants from Bangladesh.